Thickness and metallization layer effect on interfacial and vertical cracking of sintered silver layer: A numerical investigation

Abstract

Cracking of sintered silver layer always leads to the reliability issues in power devices. In this paper, the cracking behaviors of sintered silver layer have been investigated through numerical analysis with fracture based method. Energy release rate of various interfacial cracks and vertical cracks in sintered silver are computed. It is found that the energy release rate of interfacial crack and vertical crack are significantly influenced by their thickness. The thinner of the sintered silver layer, the higher of the energy release rate it will meet. For interfacial crack, the adding of the metallization layer does not improve the energy release rate significantly. For vertical crack, two conditions are considered, i.e., vertical crack emanating from the chip sider or emanating from the copper baseplate side, and it is found that the energy release rate is strongly dependent on its location and the existence of metallization layer. The increase of the thickness of Ni layer enables to lower down the entire level of energy release rate for vertical crack. Otherwise, the energy release rate of vertical crack near the edge region of the sintered silver layer is much higher than other locations. It implies that the cracking risk is higher for thinner sintered silver layer around the edge region which should be avoided. It is also found that the porosity effect on interface cracking and vertical cracking of sintered silver is also important.